Traditional aerobic base training needs to go the way of the dodo. Long, moderate intensity rides are fun and good to incorporate into training, but even if you’re a pro it is a fool’s errand to devote the winter to low-intensity training in the hopes of building a stronger aerobic base. For the rest of us who are time-crunched amateur racers and enthusiasts, traditional base training is a waste of time. The premise of aerobic base training is that accumulating a large volume of work at a low to moderate intensity will result in increased capillary density (greater perfusion of oxygenated blood into muscles) and greater mitochondrial density. The latter is important because more and bigger mitochondria in muscle cells increase your capacity to break down carbohydrate and fat into usable energy more quickly. Processing more fat and carbohydrate per minute through mitochondria increases maximum sustainable power or pace. It also means you can operate at a lower percentage of your VO2 max at your “all day” pace, which may help you rely on a higher percentage of fat for energy and conserve stored carbohydrate. Those sound like the exact goals of endurance training, so what’s the problem?